The present invention relates to an optometric apparatus for subjectively examining the visual function of an eye to be examined.
In an examination for prescribing spectacle lenses or the like, a subjective-type refractive-power examining device is used which has a pair of left and right optical units in which various corrective optical systems are adapted to be selectively disposed in a pair of test windows. When a correction power for far use of an eye to be examined is examined, the eye to be examined is caused to observe a target for far use through the corrective optical system, and the corrective optical system is adjusted on the basis of a response from a subject so as to obtain a power.
When correction for near use is required, a signal for an addition power mode is inputted to operate a flapping mechanism provided in the subjective-type refractive-power examining device, so as to flap (converge) the pair of left and right optical units. In this flapped state, a target for near use is presented to the eye to be examined at a predetermined examination distance for near use, so as to obtain an addition power with respect to the correction power for far use.
With the conventional apparatus, however, if the addition power mode is canceled, the optical system with the addition power is canceled, and the optical units which are in the flapped state are returned to the state of far vision. Complicated operations have been required when it is desirable to allow the subject requiring correction for near use to confirm the appearance of the target for near use in the state of correction for far use. The determination of the extent to which the target for near use is difficult to view in the state of correction for far use depends on the memory of the subject, but this determination has been impossible to effect promptly.
In addition, the addition power obtained by the conventional apparatus is for a predetermined examination distance for near use. However, there are cases where a near-work distance which the subject actually requires varies from the examination distance for near use. In this case, the adjustment of the addition power obtained in the examination to the power at the near-work distance required by the subject is complicated in terms of its processing, and is time-consuming, so that the burden imposed on the examiner is large.
In addition, the results of examination for far use and near use have conventionally been printed out in the form of prescription values for far use and addition power. Although no problem is encountered if the lenses to be prescribed are bifocal, in a case where lenses exclusively used for near use are required, it has been necessary for the examiner to conduct processing in which an addition power portion is added to the spherical power for far use. This operation is troublesome, and there have been cases where a problem arises such as the power of the lens becoming different due to an error in the processing.